Multichannel tape head module having thermal device for controlling span between transducers

ABSTRACT

In one embodiment, an apparatus includes a module having an array of transducers, and a heating element having multiple parts positioned proximate to the array of transducers. The multiple parts of the heating element are distinct from each other, where the multiple parts include a first part, a second part, and a third part. In addition, the first part includes a center portion and the second and third parts include a second portion and a third portion, respectively, and are positioned on opposite ends and a center portion positioned therebetween. The heating element is configured to produce more heat per unit length along the second and third portions at the opposite ends than in the center portion.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to controlling span betweentransducers of a multichannel tape head modules.

In magnetic storage systems, magnetic transducers read data from andwrite data onto magnetic recording media. Data is written on themagnetic recording media by moving a magnetic recording transducer to aposition over the media where the data is to be stored. The magneticrecording transducer then generates a magnetic field, which encodes thedata into the magnetic media. Data is read from the media by similarlypositioning the magnetic read transducer and then sensing the magneticfield of the magnetic media. Read and write operations may beindependently synchronized with the movement of the media to ensure thatthe data can be read from and written to the desired location on themedia.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly for use in such systems.

SUMMARY

In one embodiment, an apparatus includes a module having an array oftransducers, and a heating element having multiple parts positionedproximate to the array of transducers. The multiple parts of the heatingelement are distinct from each other, where the multiple parts include afirst part, a second part, and a third part. In addition, the first partincludes a center portion and the second and third parts include asecond portion and a third portion, respectively, and are positioned onopposite ends and a center portion positioned therebetween. The heatingelement is configured to produce more heat per unit length along thesecond and third portions at the opposite ends than in the centerportion.

Any of these embodiments may be implemented in a magnetic data storagesystem such as a tape drive system, which may include a magnetic head, adrive mechanism for passing a magnetic medium (e.g., recording tape)over the magnetic head, and a controller electrically coupled to themagnetic head.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1A is a schematic diagram of a simplified tape drive systemaccording to one embodiment.

FIG. 1B is a schematic diagram of a tape cartridge according to oneembodiment.

FIG. 2A illustrates a side view of a flat-lapped, bi-directional,two-module magnetic tape head according to one embodiment.

FIG. 2B is a tape bearing surface view taken from Line 2B of FIG. 2A.

FIG. 2C is a detailed view taken from Circle 2C of FIG. 2B.

FIG. 2D is a detailed view of a partial tape bearing surface of a pairof modules.

FIG. 3 is a partial tape bearing surface view of a magnetic head havinga write-read-write configuration.

FIG. 4 is a partial tape bearing surface view of a magnetic head havinga read-write-read configuration.

FIG. 5 is a side view of a magnetic tape head with three modulesaccording to one embodiment where the modules all generally lie alongabout parallel planes.

FIG. 6 is a side view of a magnetic tape head with three modules in atangent (angled) configuration.

FIG. 7 is a side view of a magnetic tape head with three modules in anoverwrap configuration.

FIGS. 8A-8C are schematics depicting the principles of tape tenting.

FIG. 9 is a representational diagram of files and indexes stored on amagnetic tape according to one embodiment.

FIG. 10A is a schematic drawing of a partial view of a module having arectangular heating element.

FIG. 10B is temperature map of the module of FIG. 10A, according tomodeling studies.

FIG. 10C is a map of thermal expansion of the module of FIG. 10A,according to modeling studies.

FIG. 11A is a schematic drawing of a partial view of a module having aheating element, according to one embodiment.

FIGS. 11B-11H are schematic drawings of various heating elements,according to various embodiments.

FIG. 12 is a flow chart of a method, according to one embodiment.

FIG. 13A is a schematic drawing of a partial view of a model having aheating element, according to one embodiment.

FIGS. 13B and 13C are schematic drawings of expansion control plates,according to various embodiments.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments ofmagnetic storage systems, as well as operation and/or component partsthereof.

In one general embodiment, an apparatus includes a module having anarray of transducers and a heating element positioned proximate to thearray of transducers. The heating element has opposite ends and a centerportion therebetween, where the heating element is configured to producemore heat per unit length along the opposite ends than in the centerportion.

In another general embodiment, a method of maintaining a span of anarray of transducers of a module to a target based on a specification isprovided. The method includes determining whether the span of the arrayof transducers in a module is different than a target based on aspecification, and in response to determining the span is less than thetarget, applying a current to a heating element positioned proximate tothe span of the array of transducers for expanding the span of the arrayof transducers toward the target. The heating element is configured tosubstantially uniformly heat the module along the heating element.

In yet another general embodiment, an apparatus includes a module havingan array of transducers, a heating element positioned proximate to thearray of transducers, and an expansion control plate configured toprovide a generally uniform thermal expansion of the array oftransducers in association with the heating element.

FIG. 1A illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1A, it should be noted that the embodiments described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cartridge and are not necessarily part of the system 100.The tape drive, such as that illustrated in FIG. 1A, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type. Suchhead may include an array of readers, writers, or both.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller 128 via a cable 130. Thecontroller 128, may be or include a processor and/or any logic forcontrolling any subsystem of the drive 100. For example, the controller128 typically controls head functions such as servo following, datawriting, data reading, etc. The controller 128 may include at least oneservo channel and at least one data channel, each of which include dataflow processing logic configured to process and/or store information tobe written to and/or read from the tape 122. The controller 128 mayoperate under logic known in the art, as well as any logic disclosedherein, and thus may be considered as a processor for any of thedescriptions of tape drives included herein, in various embodiments. Thecontroller 128 may be coupled to a memory 136 of any known type, whichmay store instructions executable by the controller 128. Moreover, thecontroller 128 may be configured and/or programmable to perform orcontrol some or all of the methodology presented herein. Thus, thecontroller 128 may be considered to be configured to perform variousoperations by way of logic programmed into one or more chips, modules,and/or blocks; software, firmware, and/or other instructions beingavailable to one or more processors; etc., and combinations thereof.

The cable 130 may include read/write circuits to transmit data to thehead 126 to be recorded on the tape 122 and to receive data read by thehead 126 from the tape 122. An actuator 132 controls position of thehead 126 relative to the tape 122.

An interface 134 may also be provided for communication between the tapedrive 100 and a host (internal or external) to send and receive the dataand for controlling the operation of the tape drive 100 andcommunicating the status of the tape drive 100 to the host, all as willbe understood by those of skill in the art.

FIG. 1B illustrates an exemplary tape cartridge 150 according to oneembodiment. Such tape cartridge 150 may be used with a system such asthat shown in FIG. 1A. As shown, the tape cartridge 150 includes ahousing 152, a tape 122 in the housing 152, and a nonvolatile memory 156coupled to the housing 152. In some approaches, the nonvolatile memory156 may be embedded inside the housing 152, as shown in FIG. 1B. In moreapproaches, the nonvolatile memory 156 may be attached to the inside oroutside of the housing 152 without modification of the housing 152. Forexample, the nonvolatile memory may be embedded in a self-adhesive label154. In one preferred embodiment, the nonvolatile memory 156 may be aFlash memory device, read-only memory (ROM) device, etc., embedded intoor coupled to the inside or outside of the tape cartridge 150. Thenonvolatile memory is accessible by the tape drive and the tapeoperating software (the driver software), and/or another device.

By way of example, FIG. 2A illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of the present invention. As shown, the headincludes a pair of bases 202, each equipped with a module 204, and fixedat a small angle α with respect to each other. The bases may be“U-beams” that are adhesively coupled together. Each module 204 includesa substrate 204A and a closure 204B with a thin film portion, commonlyreferred to as a “gap” in which the readers and/or writers 206 areformed. In use, a tape 208 is moved over the modules 204 along a media(tape) bearing surface 209 in the manner shown for reading and writingdata on the tape 208 using the readers and writers. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media supportsurfaces 209 are usually between about 0.1 degree and about 3 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B may be made of the sameor similar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), wherein the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo track readers for reading servo data on the medium.

FIG. 2B illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2B of FIG. 2A. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4 to 32 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2B on a one-halfinch wide tape 208. The data bands are defined between servo tracks 210.Each data band may include a number of data tracks, for example 1024data tracks (not shown). During read/write operations, the readersand/or writers 206 are positioned to specific track positions within oneof the data bands. Outer readers, sometimes called servo readers, readthe servo tracks 210. The servo signals are in turn used to keep thereaders and/or writers 206 aligned with a particular set of tracksduring the read/write operations.

FIG. 2C depicts a plurality of readers and/or writers 206 formed in agap 218 on the module 204 in Circle 2C of FIG. 2B. As shown, the arrayof readers and writers 206 includes, for example, 16 writers 214, 16readers 216 and two servo readers 212, though the number of elements mayvary. Illustrative embodiments include 8, 16, 32, 40, and 64 activereaders and/or writers 206 per array, and alternatively interleaveddesigns having odd numbers of reader or writers such as 17, 25, 33, etc.An illustrative embodiment includes 32 readers per array and/or 32writers per array, where the actual number of transducer elements couldbe greater, e.g., 33, 34, etc. This allows the tape to travel moreslowly, thereby reducing speed-induced tracking and mechanicaldifficulties and/or execute fewer “wraps” to fill or read the tape.While the readers and writers may be arranged in a piggybackconfiguration as shown in FIG. 2C, the readers 216 and writers 214 mayalso be arranged in an interleaved configuration. Alternatively, eacharray of readers and/or writers 206 may be readers or writers only, andthe arrays may contain one or more servo readers 212. As noted byconsidering FIGS. 2A and 2B-2C together, each module 204 may include acomplementary set of readers and/or writers 206 for such things asbi-directional reading and writing, read-while-write capability,backward compatibility, etc.

FIG. 2D shows a partial tape bearing surface view of complementarymodules of a magnetic tape head 200 according to one embodiment. In thisembodiment, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write transducer 214 and the readers, exemplified by the readtransducer 216, are aligned parallel to an intended direction of travelof a tape medium thereacross to form an R/W pair, exemplified by the R/Wpair 222. Note that the intended direction of tape travel is sometimesreferred to herein as the direction of tape travel, and such terms maybe used interchangeably. Such direction of tape travel may be inferredfrom the design of the system, e.g., by examining the guides; observingthe actual direction of tape travel relative to the reference point;etc. Moreover, in a system operable for bi-direction reading and/orwriting, the direction of tape travel in both directions is typicallyparallel and thus both directions may be considered equivalent to eachother.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked magnetoresistive (MR) headassembly 200 includes two thin-film modules 224 and 226 of generallyidentical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe (−),cobalt zirconium tantalum (CZT) or Al—Fe—Si (Sendust), a sensor 234 forsensing a data track on a magnetic medium, a second shield 238 typicallyof a nickel-iron alloy (e.g., ˜80/20 at % NiFe, also known aspermalloy), first and second writer pole tips 228, 230, and a coil (notshown). The sensor may be of any known type, including those based onMR, GMR, AMR, tunneling magnetoresistance (TMR), etc.

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as ˜45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

The configuration of the tape head 126 according to one embodimentincludes multiple modules, preferably three or more. In awrite-read-write (W-R-W) head, outer modules for writing flank one ormore inner modules for reading. Referring to FIG. 3, depicting a W-R-Wconfiguration, the outer modules 252, 256 each include one or morearrays of writers 260. The inner module 254 of FIG. 3 includes one ormore arrays of readers 258 in a similar configuration. Variations of amulti-module head include a R-W-R head (FIG. 4), a R-R-W head, a W-W-Rhead, etc. In yet other variations, one or more of the modules may haveread/write pairs of transducers. Moreover, more than three modules maybe present. In further approaches, two outer modules may flank two ormore inner modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. Forsimplicity, a W-R-W head is used primarily herein to exemplifyembodiments of the present invention. One skilled in the art apprisedwith the teachings herein will appreciate how permutations of thepresent invention would apply to configurations other than a W-R-Wconfiguration.

FIG. 5 illustrates a magnetic head 126 according to one embodiment ofthe present invention that includes first, second and third modules 302,304, 306 each having a tape bearing surface 308, 310, 312 respectively,which may be flat, contoured, etc. Note that while the term “tapebearing surface” appears to imply that the surface facing the tape 315is in physical contact with the tape bearing surface, this is notnecessarily the case. Rather, only a portion of the tape may be incontact with the tape bearing surface, constantly or intermittently,with other portions of the tape riding (or “flying”) above the tapebearing surface on a layer of air, sometimes referred to as an “airbearing”. The first module 302 will be referred to as the “leading”module as it is the first module encountered by the tape in a threemodule design for tape moving in the indicated direction. The thirdmodule 306 will be referred to as the “trailing” module. The trailingmodule follows the middle module and is the last module seen by the tapein a three module design. The leading and trailing modules 302, 306 arereferred to collectively as outer modules. Also note that the outermodules 302, 306 will alternate as leading modules, depending on thedirection of travel of the tape 315.

In one embodiment, the tape bearing surfaces 308, 310, 312 of the first,second and third modules 302, 304, 306 lie on about parallel planes(which is meant to include parallel and nearly parallel planes, e.g.,between parallel and tangential as in FIG. 6), and the tape bearingsurface 310 of the second module 304 is above the tape bearing surfaces308, 312 of the first and third modules 302, 306. As described below,this has the effect of creating the desired wrap angle α₂ of the taperelative to the tape bearing surface 310 of the second module 304.

Where the tape bearing surfaces 308, 310, 312 lie along parallel ornearly parallel yet offset planes, intuitively, the tape should peel offof the tape bearing surface 308 of the leading module 302. However, thevacuum created by the skiving edge 318 of the leading module 302 hasbeen found by experimentation to be sufficient to keep the tape adheredto the tape bearing surface 308 of the leading module 302. The trailingedge 320 of the leading module 302 (the end from which the tape leavesthe leading module 302) is the approximate reference point which definesthe wrap angle α₂ over the tape bearing surface 310 of the second module304. The tape stays in close proximity to the tape bearing surface untilclose to the trailing edge 320 of the leading module 302. Accordingly,read and/or write elements 322 may be located near the trailing edges ofthe outer modules 302, 306. These embodiments are particularly adaptedfor write-read-write applications.

A benefit of this and other embodiments described herein is that,because the outer modules 302, 306 are fixed at a determined offset fromthe second module 304, the inner wrap angle α₂ is fixed when the modules302, 304, 306 are coupled together or are otherwise fixed into a head.The inner wrap angle α₂ is approximately tan⁻¹(δ/W) where δ is theheight difference between the planes of the tape bearing surfaces 308,310 and W is the width between the opposing ends of the tape bearingsurfaces 308, 310. An illustrative inner wrap angle α₂ is in a range ofabout 0.3° to about 1.1°, though can be any angle required by thedesign.

Beneficially, the inner wrap angle α₂ on the side of the module 304receiving the tape (leading edge) will be larger than the inner wrapangle α₃ on the trailing edge, as the tape 315 rides above the trailingmodule 306. This difference is generally beneficial as a smaller α₃tends to oppose what has heretofore been a steeper exiting effectivewrap angle.

Note that the tape bearing surfaces 308, 312 of the outer modules 302,306 are positioned to achieve a negative wrap angle at the trailing edge320 of the leading module 302. This is generally beneficial in helpingto reduce friction due to contact with the trailing edge 320, providedthat proper consideration is given to the location of the crowbar regionthat forms in the tape where it peels off the head. This negative wrapangle also reduces flutter and scrubbing damage to the elements on theleading module 302. Further, at the trailing module 306, the tape 315flies over the tape bearing surface 312 so there is virtually no wear onthe elements when tape is moving in this direction. Particularly, thetape 315 entrains air and so will not significantly ride on the tapebearing surface 312 of the third module 306 (some contact may occur).This is permissible, because the leading module 302 is writing while thetrailing module 306 is idle.

Writing and reading functions are performed by different modules at anygiven time. In one embodiment, the second module 304 includes aplurality of data and optional servo readers 331 and no writers. Thefirst and third modules 302, 306 include a plurality of writers 322 andno data readers, with the exception that the outer modules 302, 306 mayinclude optional servo readers. The servo readers may be used toposition the head during reading and/or writing operations. The servoreader(s) on each module are typically located towards the end of thearray of readers or writers.

By having only readers or side by side writers and servo readers in thegap between the substrate and closure, the gap length can besubstantially reduced. Typical heads have piggybacked readers andwriters, where the writer is formed above each reader. A typical gap is20-35 microns. However, irregularities on the tape may tend to droopinto the gap and create gap erosion. Thus, the smaller the gap is thebetter. The smaller gap enabled herein exhibits fewer wear relatedproblems.

In some embodiments, the second module 304 has a closure, while thefirst and third modules 302, 306 do not have a closure. Where there isno closure, preferably a hard coating is added to the module. Onepreferred coating is diamond-like carbon (DLC).

In the embodiment shown in FIG. 5, the first, second, and third modules302, 304, 306 each have a closure 332, 334, 336, which extends the tapebearing surface of the associated module, thereby effectivelypositioning the read/write elements away from the edge of the tapebearing surface. The closure 332 on the second module 304 can be aceramic closure of a type typically found on tape heads. The closures334, 336 of the first and third modules 302, 306, however, may beshorter than the closure 332 of the second module 304 as measuredparallel to a direction of tape travel over the respective module. Thisenables positioning the modules closer together. One way to produceshorter closures 334, 336 is to lap the standard ceramic closures of thesecond module 304 an additional amount. Another way is to plate ordeposit thin film closures above the elements during thin filmprocessing. For example, a thin film closure of a hard material such asSendust or nickel-iron alloy (e.g., 45/55) can be formed on the module.

With reduced-thickness ceramic or thin film closures 334, 336 or noclosures on the outer modules 302, 306, the write-to-read gap spacingcan be reduced to less than about 1 mm, e.g., about 0.75 mm, or 50% lessthan commonly-used linear tape open (LTO) tape head spacing. The openspace between the modules 302, 304, 306 can still be set toapproximately 0.5 to 0.6 mm, which in some embodiments is ideal forstabilizing tape motion over the second module 304.

Depending on tape tension and stiffness, it may be desirable to anglethe tape bearing surfaces of the outer modules relative to the tapebearing surface of the second module. FIG. 6 illustrates an embodimentwhere the modules 302, 304, 306 are in a tangent or nearly tangent(angled) configuration. Particularly, the tape bearing surfaces of theouter modules 302, 306 are about parallel to the tape at the desiredwrap angle α₂ of the second module 304. In other words, the planes ofthe tape bearing surfaces 308, 312 of the outer modules 302, 306 areoriented at about the desired wrap angle α₂ of the tape 315 relative tothe second module 304. The tape will also pop off of the trailing module306 in this embodiment, thereby reducing wear on the elements in thetrailing module 306. These embodiments are particularly useful forwrite-read-write applications. Additional aspects of these embodimentsare similar to those given above.

Typically, the tape wrap angles may be set about midway between theembodiments shown in FIGS. 5 and 6.

FIG. 7 illustrates an embodiment where the modules 302, 304, 306 are inan overwrap configuration. Particularly, the tape bearing surfaces 308,312 of the outer modules 302, 306 are angled slightly more than the tape315 when set at the desired wrap angle α₂ relative to the second module304. In this embodiment, the tape does not pop off of the trailingmodule, allowing it to be used for writing or reading. Accordingly, theleading and middle modules can both perform reading and/or writingfunctions while the trailing module can read any just-written data.Thus, these embodiments are preferred for write-read-write,read-write-read, and write-write-read applications. In the latterembodiments, closures should be wider than the tape canopies forensuring read capability. The wider closures may require a widergap-to-gap separation. Therefore, a preferred embodiment has awrite-read-write configuration, which may use shortened closures thatthus allow closer gap-to-gap separation.

Additional aspects of the embodiments shown in FIGS. 6 and 7 are similarto those given above.

A 32 channel version of a multi-module head 126 may use cables 350having leads on the same or smaller pitch as current 16 channelpiggyback LTO modules, or alternatively the connections on the modulemay be organ-keyboarded for a 50% reduction in cable span. Over-under,writing pair unshielded cables may be used for the writers, which mayhave integrated servo readers.

The outer wrap angles α₁ may be set in the drive, such as by guides ofany type known in the art, such as adjustable rollers, slides, etc. oralternatively by outriggers, which are integral to the head. Forexample, rollers having an offset axis may be used to set the wrapangles. The offset axis creates an orbital arc of rotation, allowingprecise alignment of the wrap angle α₁.

To assemble any of the embodiments described above, conventional u-beamassembly can be used. Accordingly, the mass of the resultant head may bemaintained or even reduced relative to heads of previous generations. Inother approaches, the modules may be constructed as a unitary body.Those skilled in the art, armed with the present teachings, willappreciate that other known methods of manufacturing such heads may beadapted for use in constructing such heads. Moreover, unless otherwisespecified, processes and materials of types known in the art may beadapted for use in various embodiments in conformance with the teachingsherein, as would become apparent to one skilled in the art upon readingthe present disclosure.

As a tape is run over a module, it is preferred that the tape passessufficiently close to magnetic transducers on the module such thatreading and/or writing is efficiently performed, e.g., with a low errorrate. According to some approaches, tape tenting may be used to ensurethe tape passes sufficiently close to the portion of the module havingthe magnetic transducers. To better understand this process, FIGS. 8A-8Cillustrate the principles of tape tenting. FIG. 8A shows a module 800having an upper tape bearing surface 802 extending between oppositeedges 804, 806. A stationary tape 808 is shown wrapping around the edges804, 806. As shown, the bending stiffness of the tape 808 lifts the tapeoff of the tape bearing surface 802. Tape tension tends to flatten thetape profile, as shown in FIG. 8A. Where tape tension is minimal, thecurvature of the tape is more parabolic than shown.

FIG. 8B depicts the tape 808 in motion. The leading edge, i.e., thefirst edge the tape encounters when moving, may serve to skive air fromthe tape, thereby creating a subambient air pressure between the tape808 and the tape bearing surface 802. In FIG. 8B, the leading edge isthe left edge and the right edge is the trailing edge when the tape ismoving left to right. As a result, atmospheric pressure above the tapeurges the tape toward the tape bearing surface 802, thereby creatingtape tenting proximate each of the edges. The tape bending stiffnessresists the effect of the atmospheric pressure, thereby causing the tapetenting proximate both the leading and trailing edges. Modeling predictsthat the two tents are very similar in shape.

FIG. 8C depicts how the subambient pressure urges the tape 808 towardthe tape bearing surface 802 even when a trailing guide 810 ispositioned above the plane of the tape bearing surface.

It follows that tape tenting may be used to direct the path of a tape asit passes over a module. As previously mentioned, tape tenting may beused to ensure the tape passes sufficiently close to the portion of themodule having the magnetic transducers, preferably such that readingand/or writing is efficiently performed, e.g., with a low error rate.

Magnetic tapes may be stored in tape cartridges that are, in turn,stored at storage slots or the like inside a data storage library. Thetape cartridges may be stored in the library such that they areaccessible for physical retrieval. In addition to magnetic tapes andtape cartridges, data storage libraries may include data storage drivesthat store data to, and/or retrieve data from, the magnetic tapes.Moreover, tape libraries and the components included therein mayimplement a file system which enables access to tape and data stored onthe tape.

File systems may be used to control how data is stored in, and retrievedfrom, memory. Thus, a file system may include the processes and datastructures that an operating system uses to keep track of files inmemory, e.g., the way the files are organized in memory. Linear TapeFile System (LTFS) is an exemplary format of a file system that may beimplemented in a given library in order to enables access to complianttapes. It should be appreciated that various embodiments herein can beimplemented with a wide range of file system formats, including forexample IBM Spectrum Archive Library Edition (LTFS LE). However, toprovide a context, and solely to assist the reader, some of theembodiments below may be described with reference to LTFS which is atype of file system format. This has been done by way of example only,and should not be deemed limiting on the invention defined in theclaims.

A tape cartridge may be “loaded” by inserting the cartridge into thetape drive, and the tape cartridge may be “unloaded” by removing thetape cartridge from the tape drive. Once loaded in a tape drive, thetape in the cartridge may be “threaded” through the drive by physicallypulling the tape (the magnetic recording portion) from the tapecartridge, and passing it above a magnetic head of a tape drive.Furthermore, the tape may be attached on a take-up reel (e.g., see 121of FIG. 1A above) to move the tape over the magnetic head.

Once threaded in the tape drive, the tape in the cartridge may be“mounted” by reading metadata on a tape and bringing the tape into astate where the LTFS is able to use the tape as a constituent componentof a file system. Moreover, in order to “unmount” a tape, metadata ispreferably first written on the tape (e.g., as an index), after whichthe tape may be removed from the state where the LTFS is allowed to usethe tape as a constituent component of a file system. Finally, to“unthread” the tape, the tape is unattached from the take-up reel and isphysically placed back into the inside of a tape cartridge again. Thecartridge may remain loaded in the tape drive even after the tape hasbeen unthreaded, e.g., waiting for another read and/or write request.However, in other instances, the tape cartridge may be unloaded from thetape drive upon the tape being unthreaded, e.g., as described above.

Magnetic tape is a sequential access medium. Thus, new data is writtento the tape by appending the data at the end of previously written data.It follows that when data is recorded in a tape having only onepartition, metadata (e.g., allocation information) is continuouslyappended to an end of the previously written data as it frequentlyupdates and is accordingly rewritten to tape. As a result, the rearmostinformation is read when a tape is first mounted in order to access themost recent copy of the metadata corresponding to the tape. However,this introduces a considerable amount of delay in the process ofmounting a given tape.

To overcome this delay caused by single partition tape mediums, the LTFSformat includes a tape that is divided into two partitions, whichinclude an index partition and a data partition. The index partition maybe configured to record metadata (meta information), e.g., such as fileallocation information (Index), while the data partition may beconfigured to record the body of the data, e.g., the data itself.

Looking to FIG. 9, a magnetic tape 900 having an index partition 902 anda data partition 904 is illustrated according to one embodiment. Asshown, data files and indexes are stored on the tape. The LTFS formatallows for index information to be recorded in the index partition 902at the beginning of tape 906, as would be appreciated by one skilled inthe art upon reading the present description.

As index information is updated, it preferably overwrites the previousversion of the index information, thereby allowing the currently updatedindex information to be accessible at the beginning of tape in the indexpartition. According to the specific example illustrated in FIG. 9, amost recent version of metadata Index 3 is recorded in the indexpartition 902 at the beginning of the tape 906. Conversely, all threeversion of metadata Index 1, Index 2, Index 3 as well as data File A,File B, File C, File D are recorded in the data partition 904 of thetape. Although Index 1 and Index 2 are old (e.g., outdated) indexes,because information is written to tape by appending it to the end of thepreviously written data as described above, these old indexes Index 1,Index 2 remain stored on the tape 900 in the data partition 904 withoutbeing overwritten.

The metadata may be updated in the index partition 902 and/or the datapartition 904 the same or differently depending on the desiredembodiment. According to some embodiments, the metadata of the indexand/or data partitions 902, 904 may be updated in response to the tapebeing unmounted, e.g., such that the index may be read quickly from theindex partition when that tape is mounted again. The metadata ispreferably also written in the data partition 904 so the tape may bemounted using the metadata recorded in the data partition 904, e.g., asa backup option.

According to one example, which is no way intended to limit theinvention, LTFS LE may be used to provide the functionality of writingan index in the data partition when a user explicitly instructs thesystem to do so, or at a time designated by a predetermined period whichmay be set by the user, e.g., such that data loss in the event of suddenpower stoppage can be mitigated.

As noted above, a continuing goal of the data storage industry is toimprove data density, such as by reducing track width. However,limitations in head manufacturing result in variation in span of tracksfrom head-to-head, thereby leading to limits of a real density due tothe resulting misplacement of tracks during writing. Moreover, suchmisplacement of written tracks present future repercussions in that itaffects reading such data. Thus, the variation of span between channelsfrom head-to-head is a serious problem. For instance, even thoughmanufactured to exacting specifications on a single wafer, head spanbetween outermost transducers can vary from head-to-head by as much as600 nanometers (nm) or more in current generation LTO heads that aredesigned for writing and reading one-half inch, 4 data band magneticrecording tapes.

In one embodiment described herein, in a module, the span of datatransducers and servo reading elements that flank the data transducersmay be altered by a control element. In some approaches, a closed loopfeedback circuit may facilitate the control element.

In some embodiments, a head module may be comprised of a thin filmresistive element positioned proximate to the transducers and coupled toa source of electrical current. When current flows through the resistiveelement, the temperature of the resistive element rises due to jouleheating, which in turn raises the temperature of the module in thevicinity of the element. The increased temperature of and around theelement induces thermal expansion of the heated region and thus anincrease in the span of data transducers of the module.

In a preferred embodiment, a control circuit adjusts power in theheating element to maintain a constant or near constant span length,e.g., a target length based on a specification such as LTO. In someapproaches, the target span of the data transducers may be apre-determined value, e.g., a design value.

In other approaches, the proper transducer spacing and/or array lengthmay be determined as a function of the state of lateral expansion of thetape, e.g., if the tape is in a laterally expanded state relative to thestate when it was written, the array length may be increased.Accordingly, comparing the timing detected by servo readers flanking thearray of data transducers to the timing when the tape was written mayindicate a change in the tape expansion or a change in head span orboth, and thereby prompting an adjustment of the heating element tocontrol the heat to the region.

The rise in temperature and thus the change in span of transducers is afunction of several factors, including power dissipation in theresistive element, design of the resistive element, the precise locationof the resistive element in the head module, tape velocity, head landsdesign, heat dissipation in the module, etc., the effect of each ofwhich may be determined via modeling. Moreover, a magnetic recordingtape moving over a head module effectively removes heat generated by theheating element. In some embodiments, the speed of the moving magneticrecording tape may be adjusted by the controller to alter head span.Generally, lower speeds of a moving magnetic recording tape results inhigher temperature rise for a given heater power compared to a lowertemperature rise by higher speeds of the moving magnetic recording tape.The moving magnetic recording tape may also become heated therebyresulting in tape expansion. Tape expansion due to increased heat maywork against the heat-mediated expansion of the head span. Typically,however, the tape expands in response to increased temperature.Moreover, tape expansion due to heating may also be a function of tapespeed, for a given power of heat generated by the resistive element.

FIG. 10A depicts a schematic diagram of an apparatus 1000 having aresistive heating element to control span between channels, inaccordance with one embodiment. As an option, the present apparatus 1000may be implemented in conjunction with features from any otherembodiment listed herein, such as those described with reference to theother FIGS. Of course, however, such apparatus 1000 and others presentedherein may be used in various applications and/or in permutations whichmay or may not be specifically described in the illustrative embodimentslisted herein. Further, the apparatus 1000 presented herein may be usedin any desired environment.

FIG. 10A illustrates a schematic drawing of an apparatus 1000 having aresistive heating element 1010 aligned along a longitudinal axis of thespan 1006 of the array of transducers 1008, according to one embodiment.As shown, the resistive heating element 1010 may be positioned above thesubstrate 1002 in the thin films between the substrate 1002 and theclosure 1004 of the head module. The resistive heating element may bepositioned below (recessed from) the tape bearing surface 1012. In someapproaches, the resistive heating element 1010 may be offset above thesubstrate 1002 (e.g. offset approximately 1-5 microns, e.g., 3 micronsabove the substrate).

The heating element 1010 may be constructed of any conductive materialthat creates joule heating upon passing a current therethrough. Leadsfor connecting the heating element 1010 to a controller cable may befabricated in the thin films. One skilled in the art, once apprised ofthe teachings herein, would appreciate that conventional techniques andmaterials may be adapted for use in fabricating the heating element,surrounding layers, and leads.

FIG. 10B illustrates a predictive temperature rise in the module 1000with heat generated from the resistive heating element 1010. A partialview of the module is shown with the substrate 1002 facing to the rightand the closure 1004 toward the left of the schematic drawing. Asexpected with a rectangular shaped resistive heating element 1010, thetemperature is greatest near the center of the span 1006 of the array.FIG. 10B shows the highest temperature as a first region 1020 depictedby the dark shading where the first region 1020 is positioned near thetape bearing surface 1012 and around the region of the span 1006 of thearray of transducers 1008. In the illustrative predictive modeling studyshown, the first heated region 1020 depicted by the dark shading may beat a temperature of about 78° C. for an ambient temperature of 30° C.

A temperature gradient in the module is represented in the drawing bythe lines drawn crosswise on the module. The second heated region 1022,but not having a temperature as high as the dark shaded region 1020,surrounds the dark shaded region 1020 and may extend through the modulein a cross-wise direction. In predictive modeling studies the secondheated region 1022 may be about 64° C. Heated regions spreading out fromthe resistive heating element 1010 and the span 1006 of the array oftransducers 1008 may include a 3^(rd) heated region 1024, a 4^(th)heated region 1026, a 5^(th) heated region 1028, a 6^(th) heated region1030, and so on. In predictive modeling studies the temperatures ofthese regions may be approximately 60° C., 55.5° C., 51° C., 47° C.,respectively, relative to the temperature of 78° C. of the first heatedregion 1020. Again, these temperatures are presented by way of exampleonly for exemplary purposes only.

As is apparent from these modeling studies of a rectangular resistiveheating element, the heat from the element produces a nonuniformtemperature profile across the span 1006 of the array of transducers1008, and in fact, a concentration of heat is generated toward thecenter of the array of transducers, resulting in the local “hot spot”toward the center.

FIG. 10C depicts a schematic drawing of the predictive thermal expansionper watt of heater power in the module in response to the temperaturerise generated by the resistive heating element. Similar to the drawingof FIG. 10B, a partial view of the module 1000 is shown with thesubstrate 1002 to the right and the closure 1004 toward the left on thedrawing of the module. As expected from the temperature gradientpredictions of FIG. 10B, the thermal expansion of the module is notlinear along the array. Rather, as shown in FIG. 10C, a non-uniformdeformation of the region of the span 1006 of the array of transducers1008 may result in response to the higher temperatures at the center ofthe array and the decreasing temperature away from the center of thearray, resulting in greater pitch between transducers toward the middleof the array than at the ends, as well as localized protrusion of thetape bearing surface. From predictive modeling studies, the deviationfrom ideal linear expansion may be 20 nm or more. Thus, the heatingelement in a rectangular shape as shown in FIG. 10A does not induceuniform expansion of the transducer region, and therefore, does not workas expected.

Thus, providing a rectangular resistive thin film heating element with auniform resistivity throughout the element may not be a favorablesolution to the problem of misregistration between channels in the headand tracks on tape. In various embodiments described herein, theresistive heating element may be re-shaped to accommodate thenon-uniform temperature rise along the span of the array of transducersand the resulting non-linear thermal expansion of the module in thisregion. According to Ohmic heating (also known as joule heating andresistive heating), in which the passage of an electric current througha conductor produces heat, heat produced by a heating element may bedefined by the following Equation 1 and Equation 2:Heat produced (Q)=resistance (R)˜current²(I²),  Equation 1Resistance (R)=resistivity (ρ)·length (L)/area (A)  Equation 2Thus, the heat produced (Q) is proportional to the resistance (R), andthe resistance (R) of a conductor is inversely proportional to thecross-sectional area (A) of the conductor. According to variousembodiments described herein, a heating element may be designed that hasa different resistance for different portions of the heating elementsuch that when current is passing from one end of the heating element tothe other, heat is generated non-uniformly, but in such a manner as toraise the temperature of the region surrounding the heating element moreuniformly than as presented in FIG. 10B. In various embodiments, therise in temperature by the heating element may result in a more uniformexpansion across the span of transducers of the module.

FIG. 11 depicts an apparatus 1100 having a resistive heating element toalter span between transducers, in accordance with one embodiment. As anoption, the present apparatus 1100 may be implemented in conjunctionwith features from any other embodiment listed herein, such as thosedescribed with reference to the other FIGS. Of course, however, suchapparatus 1100 and others presented herein may be used in variousapplications and/or in permutations which may or may not be specificallydescribed in the illustrative embodiments listed herein. Further, theapparatus 1100 presented herein may be used in any desired environment.

According to one embodiment, an apparatus includes a module having anarray of transducers and a heating element positioned proximate to thearray of transducers where the heating element has opposite ends and acenter portion therebetween. Moreover, the heating element is configuredto produce more heat per unit length along the opposite ends than perunit length along the center portion. For example, the heating elementmay have a different, e.g., higher, resistance per unit length along theopposite ends than in the center portion when a current is passing fromone end to the other, thereby e.g., causing more heat to be producedtoward the ends than in the center. Thus, in the embodiment describedherein, the heating profile of the resistive heating element in themodule may be relatively flat therealong, thereby inducing a moreuniform thermal expansion.

In one embodiment depicted in FIG. 11A, an apparatus 1100 includes amodule 1101 having an array 1106 of transducers 1108, a heating element1110 positioned proximate to the array 1106 of transducers, a substrate1102 and an optional closure 1104.

FIG. 11B shows a schematic drawing of a cross-section of the heatingelement 1110, according to one embodiment. The heating element 1110 hasopposite ends 1120, 1122 and a center portion 1124 therebetween. In someapproaches, a higher resistance per unit length along the opposite ends1120, 1122 may be established by shape.

As shown, the heating element 1110 may be wider near the center than atthe edges and thus have a higher resistance per unit length along theopposite ends 1120, 1122 than in the center portion 1124 when a currentis passing from one end to the other, thereby causing more heat to beproduced toward the ends than in the center. In some approaches, across-sectional area of the center portion 1124 may be greater than across-sectional area of each of the opposite ends 1120, 1122 as measuredperpendicular to the longitudinal axis 1126 of the heating element 1110.

In some approaches, the center portion 1124 of the heating element 1110may have a length along a longitudinal axis 1126 in a range of betweenapproximately one third of a length of the array of transducers toapproximately two thirds of the length of the array of transducers. Inother approaches, the heating element 1110 may have a length along alongitudinal axis 1126 in a range of between approximately one third orone half of a length of the array of transducers and the full length ofthe array of transducers. In yet another approach, the heating element1110 may have a length along a longitudinal axis 1126 that is greaterthan the full length of the array of transducers. In some approaches thelength of the array of transducers may include outermost datatransducers as the endpoints of the measurement. In other approaches,the length of the array of transducers may include servo transducers asthe endpoints of measurement.

In some approaches, as shown in FIG. 11C, a heating element 1132 havinga wider center portion than at the opposite ends may have a shape havingstraight edges at the opposite ends, where the opposite ends 1134, 1136thus have a higher resistance per unit length than the center portion1138 when a current is passing from one end to the other. As in otherapproaches, more heat per unit length may be produced toward the endsthan in the center of the heating element 1132.

In some approaches, as shown in FIG. 11D, the heating element 1142,having a wider center portion 1148 than at the opposite ends 1144, 1146may have a shape having edges at the opposite ends, may be formed bymasking techniques that create unique shapes where the opposite ends1144, 1146 have a higher resistance than the center portion 1148 when acurrent is passing from one end to the other.

In some approaches, the heating element is a thin film resistiveelement.

In one embodiment, the resistivity of the center portion of the heatingelement is less than the resistivity at each of the opposite ends of theheating element. As used herein, “resistivity” refers to the sheetresistivity of the described item. As shown in FIG. 11E, the resistivityof the center portion 1158 of a heating element 1152 may be less thanthe resistivity of each of the opposite ends 1154, 1156. In someapproaches, the material 1160 of the center portion 1158 may have alower resistivity than a second material 1162 of each of the oppositeends 1154, 1156. Accordingly, the heating element 1152 may be formed ofmore than one material. In another approach, the center portion 1158 orends 1154, 1156 may be doped, subjected to ion implantation, etc. forsetting the resistivity thereof.

In some approaches, the heating element may have a rectangular shape. Insome approaches, the center portion 1158 may have a length along alongitudinal axis 1126 in a range of between approximately one third ofa length of the array of transducers to approximately two thirds of thelength of the array of transducers. In some approaches the length of thearray of transducers may include data transducers as the endpoints ofthe measurement. In other approaches, the length of the array oftransducers may include servo transducers as the endpoints ofmeasurement.

In some approaches, the heating element is a thin film resistiveelement.

In one embodiment as illustrated in FIG. 11F, in heating element 1172, across-sectional area of the center portion 1178 that is greater than across-sectional area of each of the opposite ends 1174, 1176 as measuredperpendicular to the longitudinal axis 1126 of the heating element 1172.

In some approaches, e.g., as illustrated in FIG. 11F, the resistivity ofthe center portion 1178 of a heating element 1172 may be less than theresistivity of each of the opposite ends 1174, 1176. In some approaches,the material 1180 of the center portion 1178 may have less resistivitythan a second material 1182 of each of the opposite ends 1174, 1176.

In a further approach, e.g., as illustrated in FIG. 11G, a heatingelement 1192 may be comprised of multiple parts. Various portions may beconfigured to have different heat generation than other portions. In oneapproach, the resistance of the center portion 1194 or portions is lessthan the resistance of the opposite end portions 1196. In anotherapproach, the resistance and/or heat generation of the center portion1194 or portions is similar to the resistance and/or heat generation ofeach of the opposite end portions 1196. Any number of portions may bepresent. In one approach, the center portion 1194 may include severaldistinct portions, each of which generate heat.

In various approaches, the portions may be connected in series as shownin FIG. 11G. In other approaches, the portions are connected inparallel, e.g., as shown in FIG. 11H. Moreover, in some embodiments, asexemplified in FIG. 11H, the portions 1194, 1196 may be proximate toindividual transducers 1198, e.g., 32 portions may be adjacent 32transducers.

Again, this may be effected in a variety of ways. For instance, a crosssectional area of the end portions 1196 may be smaller than thecross-sectional area of the center portion 1194. In another approach, aresistivity of the center portion 1194 may be less than the resistivityof each of the opposite end portions 1196. A combination of theforegoing approaches may be implemented in a further approach.Conventional connectivity may be used to connect the end and centerportions.

In some approaches, the resistivity of the material of the differentportions of the heating element may be set by using masking layers whereportions of the heating element have more layers resulting in a thickerportion toward a center of the element, and other portions of theheating element have less layers resulting in a thinner portion of theheating element flanking the center. In one approach, the peripheralshape of the heating element along the plane of deposition may berectangular, but the thickness of the different portions of the heatingelement vary, resulting in a heating element with portions havingdifferent resistances to generate a uniform temperature profile in thesurrounding region.

Looking back to FIGS. 3 and 4, according to one embodiment, a heatingelement 270 may be positioned proximate to an array of readers 258and/or an array of writers 260. The heating element 270 may have anyconfiguration disclosed herein in various approaches.

In various embodiments described herein, the apparatus includes acontroller electrically coupled to the heating element, where thecontroller is configured to control a power level (e.g., current)applied to the heating element for controlling an extent of thermalexpansion of the module based on a current state of expansion of amagnetic recording tape moving over the module.

In various embodiments, an apparatus includes a drive mechanism forpassing a magnetic medium over the array of transducers, and acontroller electrically coupled to the heating element and the array oftransducers.

In some embodiments, during conventional head manufacturing, the span oftransducers on the wafer may be altered to better center the range ofadjustment for later expansion to accommodate variation in span oftracks during reading and writing various tapes. For example, a span ofan array of transducers on a wafer may be smaller by 50 nm, 100 nm, 150nm, or more than a design specification. The heating element, withcurrent applied, may increase the span to a nominal target value when inuse (e.g. tape running).

Moreover, in some approaches, the span of the array of transducers on awafer during manufacturing may be adjusted to better center a range ofcontrol over a predetermined ambient operation temperature range.

FIG. 12 depicts a method 1200 for maintaining a span of an array oftransducers of a module to a specification in accordance with oneembodiment. As an option, the present method 1200 may be implemented inconjunction with features from any other embodiment listed herein, suchas those described with reference to the other FIGS. Of course, however,such a method 1200 and others presented herein may be used in variousapplications and/or in permutations which may or may not be specificallydescribed in the illustrative embodiments listed herein. Further, themethod 1200 presented herein may be used in any desired environment.

Operation 1202 of method 1200 begins with determining whether the spanof the array of transducers in a module is different than a target basedon a specification. The target based on the specification may includeany type and measurement combination of measurements between anyfeatures of the module, such as a target transducer array length, adistance between outermost servo readers, an average design transducerpitch, etc. In some approaches, determining whether the span of thearray of transducers is different than the target based on thespecification includes reading at least two servo tracks of a magneticrecording tape and deriving a length of the span therefrom, andcomparing the length to a target length based on a specification. Insome approaches, the target may be based on a current state of expansionof the magnetic recording tape as would be reflected in the actualdistance between adjacent servo tracks. For example, reading servotracks of a moving magnetic recording tape indicate that the length ofthe span of the array of transducers of the module is less than thetarget of the specification of the magnetic recording tape in use,thereby indicating a possible misplacement of tracks on the magneticrecording tape.

In the absence of a cooling element in the module, a heating element mayprovide a means of increasing head span to meet the target.

In response to determining the span of the array of transducers is lessthan the target, operation 1204 includes applying a current to a heatingelement positioned proximate to the span of the array of transducers forexpanding the span of the array of transducers toward the target viainducing thermal expansion of the module. The heating element may beconfigured to uniformly heat the module along a majority of the heatingelement (e.g., 80% or more of the length of the heating element).

In some approaches, the heating element has opposite ends and a centerportion therebetween, where the heating element has a higher resistanceper unit length along the opposite ends than in the center portion. Insome approaches, the cross-sectional area of the center portion isgreater than a cross-sectional area of each of the opposite ends of theheating element.

In some approaches, the resistivity of the center portion is less than aresistivity of each of the opposite ends.

In some approaches, the span of array of transducers may be formed onthe wafer during manufacture to have a nominal proportion that issmaller than the target defined by the specification (e.g. the span onthe wafer may be smaller by 50 nm, 100 nm, 150 nm, or more than aspecification-defined target). Then when the head is in use with taperunning, a current may be applied to the heating element to increase thespan of the array of transducers to a nominal target to meet thespecification of the tape in use.

In some approaches, method 1200 may be employed to adjust the span of anarray of transducers to operate to a specification of the tape in useover a pre-determined ambient temperature range.

In some approaches, method 1200 may include adjusting tension of amoving magnetic recording tape over the array of transducers foraltering a width of the tape. Tape tension compensation may dynamicallyadjust a span of transducers on the module to minimize misregistrationwith a specific tape. For example, tapes may undergo dimensional changesduring changes in temperature and/or humidity, tape creep after writing,etc. The width of the outermost tape windings (e.g. may be as much asone-third of the tape) may undergo a contraction due to tape tension inthe outer windings.

Moreover, in a same tape cartridge, the innermost tape windings mayundergo an expansion from tape pack pressure.

The tape tends to absorb heat from the module, and therefore may itselfexpand due to the heating. Therefore, one embodiment, the state of thetape is monitored via the track following system and the amount ofheating is adjusted accordingly to maintain the proper transducer arraylength. In addition, and/or alternatively, the tape speed may beadjusted to control the amount of heat absorbed by the tape, therebyproviding a level of control over the degree of registration betweenmodule and tape.

In a further embodiment, an expansion control plate may be used toprovide a generally uniform expansion of the array of transducers inassociation with the heating element, e.g., in conjunction with theheating characteristic of the heating element. For example, referringagain to FIGS. 10A-10C, the heating element creates very non-uniformexpansion due to the creation of hot spots. However, an expansioncontrol plate may be added to distribute heat away from the hot spot,provide more thermal expansion away from the hot spot, or both.

FIG. 13A depicts an apparatus 1300 having a resistive heating elementand an expansion control plate positioned proximate to the heatingelement. As an option, the present apparatus 1300 may be implemented inconjunction with features from any other embodiment listed herein, suchas those described with reference to the other FIGS. Of course, however,such apparatus 1300 and others presented herein may be used in variousapplications and/or in permutations which may or may not be specificallydescribed in the illustrative embodiments listed herein. Further, theapparatus 1300 presented herein may be used in any desired environment.

As shown, the apparatus 1300 is a modified version of the apparatus ofFIG. 10A, and therefore common elements have common numbering therewith.As shown, an expansion control plate 1302 is positioned proximate to theheating element 1010.

The expansion control plate 1302 may have any shape and/or compositionthat provides the desired effect. In general, the expansion controlplate 1302 should have a higher coefficient of thermal expansion thanother surrounding materials in the module. Moreover, the thicker theexpansion control plate 1302, the greater the expansion effect.Modeling, in conjunction with the teachings herein, may be used by oneskilled in the art to determine the appropriate size, shape andcomposition of an expansion control plate 1302 according to theparticular application, as with any other layer or device describedherein. Accordingly, for example, a rectangular heating element may beused with an expansion control plate 1302 designed to provide thedesired substantially uniform expansion, thereby avoiding the problemsset forth in the discussion of FIG. 10C above. Moreover, expansioncontrol plates 1302 may be constructed for use with any of the heatingelements described herein.

Preferred materials for the expansion control plate 1302 includenonmagnetic metals such as aluminum, though magnetic materials may beused in some approaches.

In one approach, the expansion control plate 1302 has a rectangularprofile.

In other approaches, the expansion control plate 1302 has anonrectangular profile. For example, the expansion control plate 1302may be wider in a center region than at opposite ends, as shown in FIG.13B. This design tends to draw heat away from the hot spot near thecenter of the heating element, thereby distributing the heat more evenlyso that other portions of the module expand more uniformly. Preferredmaterials for the expansion control plate 1302 in this approach arematerials with a higher thermal conductivity than surrounding materials,and a lower to moderate coefficient of thermal expansion.

In yet another approach, the expansion control plate 1302 is thinner ina center region than at opposite ends, as shown in FIG. 13C. Preferredmaterials for the expansion control plate 1302 in this approach arematerials with a relatively higher coefficient of thermal expansion,where the outer ends would expand more than the center due to the largersections.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), a ROM, anerasable programmable read-only memory (EPROM or Flash memory), a staticrandom access memory (SRAM), a portable compact disc read-only memory(CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk,a mechanically encoded device such as punch-cards or raised structuresin a groove having instructions recorded thereon, and any suitablecombination of the foregoing. A computer readable storage medium, asused herein, is not to be construed as being transitory signals per se,such as radio waves or other freely propagating electromagnetic waves,electromagnetic waves propagating through a waveguide or othertransmission media (e.g., light pulses passing through a fiber-opticcable), or electrical signals transmitted through a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Moreover, a system according to various embodiments may include aprocessor and logic integrated with and/or executable by the processor,the logic being configured to perform one or more of the process stepsrecited herein. By integrated with, what is meant is that the processorhas logic embedded therewith as hardware logic, such as an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), etc. By executable by the processor, what is meant is that thelogic is hardware logic; software logic such as firmware, part of anoperating system, part of an application program; etc., or somecombination of hardware and software logic that is accessible by theprocessor and configured to cause the processor to perform somefunctionality upon execution by the processor. Software logic may bestored on local and/or remote memory of any memory type, as known in theart. Any processor known in the art may be used, such as a softwareprocessor module and/or a hardware processor such as an ASIC, a FPGA, acentral processing unit (CPU), an integrated circuit (IC), etc.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

It will be further appreciated that embodiments of the present inventionmay be provided in the form of a service deployed on behalf of acustomer.

The inventive concepts disclosed herein have been presented by way ofexample to illustrate the myriad features thereof in a plurality ofillustrative scenarios, embodiments, and/or implementations. It shouldbe appreciated that the concepts generally disclosed are to beconsidered as modular, and may be implemented in any combination,permutation, or synthesis thereof. In addition, any modification,alteration, or equivalent of the presently disclosed features,functions, and concepts that would be appreciated by a person havingordinary skill in the art upon reading the instant descriptions shouldalso be considered within the scope of this disclosure.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. An apparatus, comprising: a module having anarray of transducers; and a heating element positioned proximate to thearray of transducers, the heating element having opposite ends and acenter portion positioned therebetween, wherein the heating element isconfigured to produce more heat per unit length along the opposite endsthan in the center portion, wherein a resistivity of the center portionis less than a resistivity of each of the opposite ends.
 2. An apparatusas recited in claim 1, wherein a first material of the center portionhas lower resistivity than a second material of each of the oppositeends.
 3. An apparatus as recited in claim 1, the center portion having alength in a range of between approximately one third of a length of thearray of transducers to approximately two thirds of the length of thearray of transducers.
 4. An apparatus as recited in claim 1, wherein theheating element is a thin film resistive element.
 5. An apparatus asrecited in claim 3, wherein the length of the array of transducersincludes data transducers as endpoints of a measurement of the length.6. An apparatus as recited in claim 1, the heating element having arectangular shape.
 7. An apparatus as recited in claim 1, comprising acontroller electrically coupled to the heating element wherein thecontroller is configured to control a power level applied to the heatingelement for controlling an extent of thermal expansion of the modulebased on a current state of expansion of a magnetic recording tapemoving over the module.
 8. An apparatus as recited in claim 1, furthercomprising: a drive mechanism for passing a magnetic medium over thearray of transducers; and a controller electrically coupled to theheating element and the array of transducers.